The present invention relates to a rotatable cutting tool, which is a component of an earth-working apparatus, used to impinge upon earth strata such as, for example, asphaltic roadway material or ore-bearing or coal-bearing earth (or mineral) formations. More specifically, the present invention pertains to such a rotatable cutting tool that includes a cutting tool body that contains a hard cutting tip at the axial forward end thereof and wherein the cutting tool body has improved strength properties.
Heretofore, a rotatable cutting tool has been used to impinge upon earth strata, such as for example, asphaltic roadway material or ore-bearing or coal-bearing earth (or mineral) formations and the like. Such a rotatable cutting tool typically comprises an elongate cutting tool body that has an axial forward end and an axial rearward end. In one embodiment of such a cutting tool, the cutting tool body has a socket at the axial forward end wherein the socket receives a hard cutting tip. In another embodiment of such a cutting tool, the cutting tool body contains a projection at the axial forward end thereof wherein the projection is received within a socket (or recess) in the hard cutting tip. In each one of the above embodiments, the hard cutting tip is affixed to the cutting tool body by brazing or the like.
As can be appreciated, during operation the entire rotatable cutting tool is typically subjected to a variety of extreme cutting forces in an abrasive and erosive environment. It would be undesirable for the cutting tool body to prematurely wear or fail (whether it be through catastrophic fracture or the like or through abrasive or erosive wear) prior to the hard cutting tip wearing to the point of its useful life. In such a circumstance, the rotatable cutting tool would have to replaced prior to the normally scheduled time for replacement. Further, the premature failure of the rotatable cutting tool would negatively impact the cutting or milling efficiency of the overall earthworking apparatus. It thus becomes apparent that it is important that the cutting tool body possess the requisite strength to maintain its integrity during the intended useful life of the rotatable cutting tool.
Heretofore, some portions of the cutting tool body have been formed via a cold-heading or cold-forming process. One exemplary patent is U.S. Pat. No. 4,627,665 to Ewing et al. that shows the cold-forming of a cutting tool body. However, it should be appreciated that a number of steps are necessary to form certain portion of the cutting tool body. For example, the puller groove is formed via a separate roll-forming operation while the socket and the axial forward portion of the rotatable cutting tool is formed via a cold-heading process. U.S. Pat. No. 6,397,652 to Sollami is another example of a patent that shows a cutting tool body formed by a cold forming process.
Other cutting tool bodies are made via a process in which at least some of the cutting tool body is manufactured through a process that includes a machining step. The puller groove is a portion of the cutting tool body that typically has been machined. While the machined puller groove performs satisfactorily, the fact that a machining process occurs tends to weaken or reduce the strength of the cutting tool body. Further, machining a portion of the cutting tool body (e.g., the puller prove) results in the loss of the material machined out of the blank (or stock material) to form the puller groove.
It can therefore be appreciated that it would be desirable to provide an improved cutting tool body that exhibits improved strength properties. It can also be appreciated that it would be desirable to provide an improved cutting tool body that avoids machining in the manufacture thereof so as to reduce the amount of raw material necessary to make the rotatable cutting tool.